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The Kingrex Headquarters HQ-01 is a headphone amplifier unit that retails for about $895. It is single ended, solid state, and two case design. I have listened extensively to a review sample for the past three or so months. In my opinion, the unit compares well to the Graham Slee Solo and is worth the asking price. The following is an outline of my review:
Equipment and Musical Selection
Aesthetics, Build Quality, and Features
Design
Sound and Listening Impressions
Thanks
[size=large]Equipment and Musical Selection
[/size] Dac: Benchmark Dac-1
Headphones: Sennheiser HD-650, Ety-4S
Audio Amplifier: Benchmark Dac-1, Graham Slee Solo 2007 Green Edition, Kingrex Headquarters HQ-01
Cables: Blue Jean Audio
Primary Music Selections: Bruckner: Symphony no 4 / Jochum, Berliner Philharmoniker; Eliza Gilkyson Land of Milk and Honey, Beautiful World; Guns and Roses Chinese Democracy; KMFDM Blitz; Nelly Furtado Loose, Whoa Nelly!; Tchaikovsky Pathetique Symphony XRCD.
From left to right: Benchmark Dac-1, Kingrex HQ-01, Graham Slee Solo
[size=large]Aesthetics, Build Quality, and Features
[/size]
[size=large]
[/size] The HQ-01 is a two unit amplifier with both units measuring a relatively modest 180 x 138 x 45mm. One unit is the power supply which connects to the headphone amplifier unit through the included DC power cord. The power supply unit has a power switch – which somewhat surprisingly is a ‘feature’ that both my Benchmark Dac-1 and Graham Slee Amp lack. Kingrex says that the amplifier uses 8 watts – so that leaving the amplifier unit on 24/7 is no problem. For users who like turning the amplifier off and on, the company suggests a 30 minute warm-up for best bloom. Like most pieces of audio equipment, I have found the amplifier does not sound its best when immediately turned on, but I found the 30 minute recommendation to be more than sufficient time for the amplifier to settle in. The power supply unit also has a small, but bright, blue LED to signal whether the unit is powered on or not. The amplifier unit has a set of RCA inputs and a set of RCA outputs on the back. On the front, the unit has the quarter inch headphone output, the volume control knob, and a selector for headphone or RCA output. There are also two blue LED’s to let the user know whether the headphone or RCA output is selected – a convenient feature for those who do not want to disturb others with speaker output by mistake.
The build quality and presentation are top-notch. Kingrex offers two styles of units – one with piano black and a red front, and the other has black matte appearance. Obviously, I received the former. In person, the piano black is shiny and luxurious. The thick aluminum front panel just exudes quality. The black DC cord fits snugly and securely. Kingrex recommends the units be placed side by side, and recommends that the units not be placed one on top of the other. First, I think the units just look better side by side. But there are more practical concerns. The front panels are deeper than the cases and so the cases would not sit right one on top of the other. In addition, Kingrex mentions the power cord would be at risk for bending and the audio signal might pick up more interference from the power supply. In general, it’s definitely an advantage to reduce noise when the power supply is as far as possible from the amplifier unit. The DC cord is rather short – so practically the units have to be close to each other. I suppose the power supply looks too snazzy to put on the floor anyways; and, honestly, I did not detect any audible change by fidgeting around the power supply to spots where the DC cord allowed. I think only the most fussy will find fault in the appearance of the HQ-01. The piano black finish does attract fingerprints (and shows dust), and the writing is silk-screened instead of engraved. These are the most minor of quibbles of what is surely an impressive looking amplifier.
[size=large]Design
[/size]The power supply is linear, which is a good thing since this type of design tends to produce a low noise output. The first stage uses the Toshiba A970/C2240 transistor and the second stage uses a MOSFET based design. The volume control uses the ALPS potentiometer. Again, this is another quality component. Overall, the design is solid state and class A with good quality parts. More interested readers can check the Kingrex website for internal pictures and more information on parts used.
[size=large]Sound and Listening Impressions
[/size]
It can be fun to look at a spiffy piece of audio equipment and ponder how the design and parts used will make for audio bliss. However, what really counts is how the unit sounds. The HQ-01 retails for $895 which puts it into a lofty spot competition-wise. I am going to primarily compare the unit to a Graham Slee Solo unit – which is a solid state amplifier that has an excellent reputation and is the best amp that I have heard. Note that I received the HQ-01 when it was fully burned in. Kingrex recommends 300 hours of burn-in before the amp sounds it best.
Before the main comparison, let’s start off with an easy comparison of the HQ-01 to the built-in amp for the Dac-1. The Dac-1 has a good quality amp – that is not the best – but is in my opinion much better than what people tend to give it credit for. The internal amp was designed by the same people who designed the fantastic dac section and Benchmark has claimed – rather optimistically -- that the internal headphone output provides all one could want. I think the built-in amp for the Dac-1 lacks resolution and the potentiometer used for the volume control could be improved. However, the internal amp has great power, and it does sound very good. If one has not heard better, the internal amp on the Benchmark Dac-1 will definitely suffice. So, how does it compare to the HQ-01? The HQ-01 is clearly on another level of sound quality. The HQ-01 has more clarity and better resolution, is less noisy when changing the volume, has better control, and so on. It is a definite upgrade. I cannot claim for others whether the difference is worth the cost of the HQ-01, but I can say that the difference is noticeable and was something I could definitely appreciate.
I have listened to the HD-650 using balanced cables directly from the XLR outputs of the Dac-1. Many listeners claim that this produces much better sound than the internal amp. I seem to be in the tiny minority in that I greatly prefer the internal amp of the Dac-1 over the XLR outputs. Using the XLR outputs directly produces the widest soundstage I have heard – significantly larger than the HQ-01 or the Solo – but I find the overall sound unnatural and not that enjoyable. I suspect that a properly designed balanced amplifier will retain the advantage in soundstage and rectify the unnaturalness in the sound. However, I have never had the opportunity to confirm my speculation. So, overall, I would say the HQ-01 is a clear winner over the direct XLR outputs of the Dac-1.
Enough with the easy competition for the HQ-01! Let’s get to the main draw and compare the HQ-01 to the Solo. There have been many tweaks to the Solo design over the past couple years. The Solo that I use has a cheap wall wart power supply and, rather amazingly, does not improve in sound with a more robust power supply according to some well-respected reviewers. I have not confirmed this fact with my own ears. Some people may be comforted knowing the HQ-01 does have a robust power supply and is light-years ahead in quality over the cell-phone charger style power supply of the Solo. Personally, I prefer to compare the resulting sound, and I try not to make assumptions of what design can or cannot sound good. The Solo’s wall wart is more convenient since it can be used internationally and is very small. However, the Solo wall wart can produce a barely audible chirping sound, where as the HQ-01 power supply is dead silent. Graham Slee offers a more robust style wall wart which produces cleaner output and never has the soft chirping sound – but it cannot be used internationally and it comes at a price.
Soundwise, the Solo and the HQ-01 are on the same level. I would not say that one amp clearly outclasses the other. Both amps produce world class sound, have very low noise floors, have good volume controls, and just plain produce audio that sounds ‘right’ and enjoyable. The differences between the two can be subtle. However, there are differences.
It easier for me to fade into the music when listening to the HQ-01. For instance, while listening to Eliza Gylkison, who is a folk singer with a sometimes raspy voice, the pluck of the guitar sounds more natural. There is a little more weight and a little more warmth to the sound. The vocals of Gylkison are also better on the HQ-01. There is something about her voice that just matches well with the HQ-01. There were a few times when I set out to listen to an album of hers with the HQ-01, intent on noting all the subtle details that I could, only to just get too absorbed in the music to care about the small nuances. I think the greatest strength of the HQ-01 is just that – allowing the listener to lose oneself in the music. When it comes to listening to Gylkison, I prefer the HQ-01.
Things do get a bit complicated -- even though the vocals of Gylkison sound better on the HQ-01 than the Solo, the vocals of Nelly Furtado sound better on the Solo. Furtado is more of a pop singer and her voice is higher than Gylkison’s. The Solo sounds extremely well on the Loose album. In fact, I would say that this album demonstrates the Solo in its best light. The vocals seem more holographic or multi-dimensional on the Solo and the energy and emotion of the music is carried through more. Furtado still sounds very good on the HQ-01, but it is a notch behind the Solo.
Listening to KMFDM, which is an industrial rock brand known for its so-called ‘ultra heavy beats’, it’s easy to tell the difference in bass production. The HQ-01 has more powerful and deeper bass than the Solo. There’s no question that lovers of bass will prefer the HQ-01. In addition, KMFDM also has a cool effect where a sound starts on the right side and then appears to circle around you to the left side. This sounds amazingly well on the HQ-01. It appears that the HQ-01 excels at reproducing the positioning of the sound. There are some nice female vocal sections on the Blitz album and the HQ-01 handles these as well as the Solo.
I also listened to some Bruckner’s 4th Symphony and Guns and Roses Chinese Democracy. The differences between the HQ-01 and the Solo in these musical genres were smaller than I expected. A general conclusion was emerging in my mind. If I wanted to sit back, relax, and fade into the music, then I prefer the HQ-01. If I wanted to dissect the music or do some ‘toe-tapping’, then I prefer the Solo. For instance, I would say the HQ-01 and the Solo sound equally well on Bruckner’s 4th Symphony. However, when I listened with the HQ-01 I just felt more inclined to relax and sit back, and while I listened to the Solo I was more inclined to keep my attention perked up. The difference was not pronounced as much in the sound, but in what I was feeling when I was listening. I think that’s why the HQ-01 sounds so good with Gylkison. When I listen to that album I want to sit back and get into the flow of the music because that’s what the music drives my emotion towards. When I listen to Furtado, the music drives me to be engaged and to tap my toes. Overall, the HQ-01 and the Solo are both excellent amps with slightly different strengths. It isn’t that some music sounds good on one amp and bad on the other – all the music sounds great on both. It’s just that the amps nudge my attention in a certain direction.
[size=large]Thanks
[/size]
I would like to thank Skylab for initially sending me the unit to review. He is very helpful and is a true asset to the Head-Fi community. I would like to thank my contact Christine Wu at Kingrex for answering my questions and allowing me the time needed to thoroughly become acquainted with the unit. And, of course, I would like to thank Head-Fi for providing a forum for me to publish my review. If anyone has any questions about my experience with this unit, please feel free to ask!
Equipment and Musical Selection
Aesthetics, Build Quality, and Features
Design
Sound and Listening Impressions
Thanks
[size=large]Equipment and Musical Selection
[/size] Dac: Benchmark Dac-1
Headphones: Sennheiser HD-650, Ety-4S
Audio Amplifier: Benchmark Dac-1, Graham Slee Solo 2007 Green Edition, Kingrex Headquarters HQ-01
Cables: Blue Jean Audio
Primary Music Selections: Bruckner: Symphony no 4 / Jochum, Berliner Philharmoniker; Eliza Gilkyson Land of Milk and Honey, Beautiful World; Guns and Roses Chinese Democracy; KMFDM Blitz; Nelly Furtado Loose, Whoa Nelly!; Tchaikovsky Pathetique Symphony XRCD.
From left to right: Benchmark Dac-1, Kingrex HQ-01, Graham Slee Solo
[size=large]Aesthetics, Build Quality, and Features
[/size]
[size=large]
[/size] The HQ-01 is a two unit amplifier with both units measuring a relatively modest 180 x 138 x 45mm. One unit is the power supply which connects to the headphone amplifier unit through the included DC power cord. The power supply unit has a power switch – which somewhat surprisingly is a ‘feature’ that both my Benchmark Dac-1 and Graham Slee Amp lack. Kingrex says that the amplifier uses 8 watts – so that leaving the amplifier unit on 24/7 is no problem. For users who like turning the amplifier off and on, the company suggests a 30 minute warm-up for best bloom. Like most pieces of audio equipment, I have found the amplifier does not sound its best when immediately turned on, but I found the 30 minute recommendation to be more than sufficient time for the amplifier to settle in. The power supply unit also has a small, but bright, blue LED to signal whether the unit is powered on or not. The amplifier unit has a set of RCA inputs and a set of RCA outputs on the back. On the front, the unit has the quarter inch headphone output, the volume control knob, and a selector for headphone or RCA output. There are also two blue LED’s to let the user know whether the headphone or RCA output is selected – a convenient feature for those who do not want to disturb others with speaker output by mistake.
The build quality and presentation are top-notch. Kingrex offers two styles of units – one with piano black and a red front, and the other has black matte appearance. Obviously, I received the former. In person, the piano black is shiny and luxurious. The thick aluminum front panel just exudes quality. The black DC cord fits snugly and securely. Kingrex recommends the units be placed side by side, and recommends that the units not be placed one on top of the other. First, I think the units just look better side by side. But there are more practical concerns. The front panels are deeper than the cases and so the cases would not sit right one on top of the other. In addition, Kingrex mentions the power cord would be at risk for bending and the audio signal might pick up more interference from the power supply. In general, it’s definitely an advantage to reduce noise when the power supply is as far as possible from the amplifier unit. The DC cord is rather short – so practically the units have to be close to each other. I suppose the power supply looks too snazzy to put on the floor anyways; and, honestly, I did not detect any audible change by fidgeting around the power supply to spots where the DC cord allowed. I think only the most fussy will find fault in the appearance of the HQ-01. The piano black finish does attract fingerprints (and shows dust), and the writing is silk-screened instead of engraved. These are the most minor of quibbles of what is surely an impressive looking amplifier.
[size=large]Design
[/size]The power supply is linear, which is a good thing since this type of design tends to produce a low noise output. The first stage uses the Toshiba A970/C2240 transistor and the second stage uses a MOSFET based design. The volume control uses the ALPS potentiometer. Again, this is another quality component. Overall, the design is solid state and class A with good quality parts. More interested readers can check the Kingrex website for internal pictures and more information on parts used.
[size=large]Sound and Listening Impressions
[/size]
It can be fun to look at a spiffy piece of audio equipment and ponder how the design and parts used will make for audio bliss. However, what really counts is how the unit sounds. The HQ-01 retails for $895 which puts it into a lofty spot competition-wise. I am going to primarily compare the unit to a Graham Slee Solo unit – which is a solid state amplifier that has an excellent reputation and is the best amp that I have heard. Note that I received the HQ-01 when it was fully burned in. Kingrex recommends 300 hours of burn-in before the amp sounds it best.
Before the main comparison, let’s start off with an easy comparison of the HQ-01 to the built-in amp for the Dac-1. The Dac-1 has a good quality amp – that is not the best – but is in my opinion much better than what people tend to give it credit for. The internal amp was designed by the same people who designed the fantastic dac section and Benchmark has claimed – rather optimistically -- that the internal headphone output provides all one could want. I think the built-in amp for the Dac-1 lacks resolution and the potentiometer used for the volume control could be improved. However, the internal amp has great power, and it does sound very good. If one has not heard better, the internal amp on the Benchmark Dac-1 will definitely suffice. So, how does it compare to the HQ-01? The HQ-01 is clearly on another level of sound quality. The HQ-01 has more clarity and better resolution, is less noisy when changing the volume, has better control, and so on. It is a definite upgrade. I cannot claim for others whether the difference is worth the cost of the HQ-01, but I can say that the difference is noticeable and was something I could definitely appreciate.
I have listened to the HD-650 using balanced cables directly from the XLR outputs of the Dac-1. Many listeners claim that this produces much better sound than the internal amp. I seem to be in the tiny minority in that I greatly prefer the internal amp of the Dac-1 over the XLR outputs. Using the XLR outputs directly produces the widest soundstage I have heard – significantly larger than the HQ-01 or the Solo – but I find the overall sound unnatural and not that enjoyable. I suspect that a properly designed balanced amplifier will retain the advantage in soundstage and rectify the unnaturalness in the sound. However, I have never had the opportunity to confirm my speculation. So, overall, I would say the HQ-01 is a clear winner over the direct XLR outputs of the Dac-1.
Enough with the easy competition for the HQ-01! Let’s get to the main draw and compare the HQ-01 to the Solo. There have been many tweaks to the Solo design over the past couple years. The Solo that I use has a cheap wall wart power supply and, rather amazingly, does not improve in sound with a more robust power supply according to some well-respected reviewers. I have not confirmed this fact with my own ears. Some people may be comforted knowing the HQ-01 does have a robust power supply and is light-years ahead in quality over the cell-phone charger style power supply of the Solo. Personally, I prefer to compare the resulting sound, and I try not to make assumptions of what design can or cannot sound good. The Solo’s wall wart is more convenient since it can be used internationally and is very small. However, the Solo wall wart can produce a barely audible chirping sound, where as the HQ-01 power supply is dead silent. Graham Slee offers a more robust style wall wart which produces cleaner output and never has the soft chirping sound – but it cannot be used internationally and it comes at a price.
Soundwise, the Solo and the HQ-01 are on the same level. I would not say that one amp clearly outclasses the other. Both amps produce world class sound, have very low noise floors, have good volume controls, and just plain produce audio that sounds ‘right’ and enjoyable. The differences between the two can be subtle. However, there are differences.
It easier for me to fade into the music when listening to the HQ-01. For instance, while listening to Eliza Gylkison, who is a folk singer with a sometimes raspy voice, the pluck of the guitar sounds more natural. There is a little more weight and a little more warmth to the sound. The vocals of Gylkison are also better on the HQ-01. There is something about her voice that just matches well with the HQ-01. There were a few times when I set out to listen to an album of hers with the HQ-01, intent on noting all the subtle details that I could, only to just get too absorbed in the music to care about the small nuances. I think the greatest strength of the HQ-01 is just that – allowing the listener to lose oneself in the music. When it comes to listening to Gylkison, I prefer the HQ-01.
Things do get a bit complicated -- even though the vocals of Gylkison sound better on the HQ-01 than the Solo, the vocals of Nelly Furtado sound better on the Solo. Furtado is more of a pop singer and her voice is higher than Gylkison’s. The Solo sounds extremely well on the Loose album. In fact, I would say that this album demonstrates the Solo in its best light. The vocals seem more holographic or multi-dimensional on the Solo and the energy and emotion of the music is carried through more. Furtado still sounds very good on the HQ-01, but it is a notch behind the Solo.
Listening to KMFDM, which is an industrial rock brand known for its so-called ‘ultra heavy beats’, it’s easy to tell the difference in bass production. The HQ-01 has more powerful and deeper bass than the Solo. There’s no question that lovers of bass will prefer the HQ-01. In addition, KMFDM also has a cool effect where a sound starts on the right side and then appears to circle around you to the left side. This sounds amazingly well on the HQ-01. It appears that the HQ-01 excels at reproducing the positioning of the sound. There are some nice female vocal sections on the Blitz album and the HQ-01 handles these as well as the Solo.
I also listened to some Bruckner’s 4th Symphony and Guns and Roses Chinese Democracy. The differences between the HQ-01 and the Solo in these musical genres were smaller than I expected. A general conclusion was emerging in my mind. If I wanted to sit back, relax, and fade into the music, then I prefer the HQ-01. If I wanted to dissect the music or do some ‘toe-tapping’, then I prefer the Solo. For instance, I would say the HQ-01 and the Solo sound equally well on Bruckner’s 4th Symphony. However, when I listened with the HQ-01 I just felt more inclined to relax and sit back, and while I listened to the Solo I was more inclined to keep my attention perked up. The difference was not pronounced as much in the sound, but in what I was feeling when I was listening. I think that’s why the HQ-01 sounds so good with Gylkison. When I listen to that album I want to sit back and get into the flow of the music because that’s what the music drives my emotion towards. When I listen to Furtado, the music drives me to be engaged and to tap my toes. Overall, the HQ-01 and the Solo are both excellent amps with slightly different strengths. It isn’t that some music sounds good on one amp and bad on the other – all the music sounds great on both. It’s just that the amps nudge my attention in a certain direction.
[size=large]Thanks
[/size]
I would like to thank Skylab for initially sending me the unit to review. He is very helpful and is a true asset to the Head-Fi community. I would like to thank my contact Christine Wu at Kingrex for answering my questions and allowing me the time needed to thoroughly become acquainted with the unit. And, of course, I would like to thank Head-Fi for providing a forum for me to publish my review. If anyone has any questions about my experience with this unit, please feel free to ask!
